Deep structure of the Median Tectonic Line revealed by an integrated seismic profiling across the Seto Inland Sea

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Trans-Seto and Shikoku seismic reflection profiling was made as a joint expedition of ERI, JAMSTEC and our research group based on this grant, the end of August, 2002. The deep crustal structure was indicated in an integrated profile of single-fold profiles. Significant results are summarized as follows :1.The subducting Philippine Sea plate (PHS) is clearly recognized as a combination of reflective layers 1+2 and transparent layer 3.2.The lower crust of the Japanese island arc is gently dipping southward and comes into contact with the PHS beneath the middle Shikoku.3.The Median Tectonic Line (MTL) is dipping at about 30 degrees and merges into the lower crust beneath the Seto Inland Sea.4.Major boundary faults, the Butsuzo Tectonic Line (BTL) and the Aki fault (AF) in the accretionary complexes are dipping northward and merges into the lower crust beneath the Seto Inland Sea.